1. Field of the Invention
The invention relates to a technique for holding a tool bit to a tip end of a driving shaft, or more particularly to a technique for selectively replacing various kinds of tool bits within a power tool.
2. Description of the Related Art
Japanese non-examined laid-open Patent Publication No. 2002-233972 and EP1819490 respectively disclose power tools which can be applied to various operations such as a cutting operation, a scraping operation or a grinding operation by selectively replacing different kinds of tool bits. Known power tool can perform such various operations by driving the tool bit to reciprocatingly swing around a driving shaft. According to this power tool, a selected tool bit is clamped and held between two clamping flanges. The tool bit clamped between the clamping flanges is prevented from moving in a circumferential direction, or locked against rotation, with respect to the clamping flanges. For this purpose, a fixing projection is formed on one of the clamping flanges and can be fitted into a projection receiving hole having a predetermined shape and formed in the tool bit.
In the above-described clamping-type holding structure, the fixing projection formed on the clamping flange and the projection receiving hole formed in the tool bit are formed to be appropriately engaged with each other. Therefore, if a projection receiving hole is not configured to correspond in shape or position to the fixing projection, a tool bit having such a projection receiving hole can not be attached to the clamping flange.